A laminated varistor and electronic device

Abstract

The present application proposes a laminated varistor and an electronic device. The laminated varistor includes a ceramic body, a plurality of internal electrodes and an external electrode; the plurality of internal electrodes are sequentially stacked in the ceramic body along a second direction, and two adjacent layers of internal electrodes are insulated by the ceramic body; the plurality of internal electrodes are respectively connected to the external electrodes; the free ends of at least some of the internal electrodes that are not connected to the external electrodes include a first vertex angle and a second vertex angle, and at least one of the first vertex angle and the second vertex angle is a rounded corner. The present application reduces the risk of the ceramic body (e.g., the vertex angle corresponding to the rounded corner) being punctured and the load failure caused thereby by providing the vertex angle of the free end of the internal electrode with a rounded corner.

Description

Technical Field

[0001] The present application relates to the technical field of varistors, and in particular to a laminated varistor and an electronic device. Background Art

[0002] Varistors are generally used in surge and transient protection circuits. When overvoltage or transient operation overvoltage in the circuit reaches the turn-on voltage of the varistor, the varistor changes from high resistance to low resistance in nanoseconds, releasing the instantaneous overcurrent caused by the abnormal voltage, while clamping the voltage within a safe range to protect the subsequent circuits, thereby protecting the equipment and components in the circuit from overvoltage shocks. The more internal electrodes there are, the better the varistor's surge protection performance, but current electronic devices tend to be miniaturized, and limited space limits the performance of varistors. Since the current is unevenly distributed inside the ceramic body of the varistor, it is often easy to break down at locations with high current density, resulting in load failure. Summary of the invention

[0003] In view of this, the present application provides a multilayer varistor and an electronic device, which can improve the problem of load failure caused by breakdown of the ceramic body due to high current.

[0004] The present application provides a multilayer varistor, characterized in that it comprises:

[0005] Ceramic body;

[0006] A plurality of internal electrodes are sequentially stacked in the ceramic body along a second direction, and two adjacent layers of the internal electrodes are insulated by the ceramic body;

[0007] The outer electrode, the plurality of inner electrodes are respectively connected to the outer electrode; at least some of the free ends of the inner electrodes not connected to the outer electrode include a first vertex angle and a second vertex angle, and at least one of the first vertex angle and the second vertex angle is a rounded corner.

[0008] Optionally, the first vertex angle is a rounded angle with a radius of R1, and 0.25 mm≦R1≦2 mm.

[0009] Optionally, the second vertex angle is a rounded angle with a radius of R2, and 0.25 mm≦R2≦2 mm.

[0010] Optionally, both the first vertex angle and the second vertex angle are rounded, and the radii of the two are equal.

[0011] Optionally, the ceramic body includes a plurality of vertex angles, and the vertex angles closest to the first vertex angle and the second vertex angle are rounded corners.

[0012] Optionally, the radius of the rounded corner of the ceramic body is smaller than or equal to the radius of the rounded corner of the most adjacent inner electrode.

[0013] Optionally, the radius of the fillet of the ceramic body is R0, and 0.2 mm≦R0≦0.5 mm.

[0014] Optionally, in the multilayer varistor, free ends of at least two of the inner electrodes are provided with rounded corners.

[0015] Optionally, the plurality of inner electrodes include a first inner electrode, a second inner electrode and a plurality of intermediate inner electrodes, the plurality of intermediate inner electrodes are arranged between the first inner electrode and the second inner electrode, and the free ends of the first inner electrode and the second inner electrode are provided with the rounded corners.

[0016] Optionally, the material of the ceramic body includes zinc oxide and oxide of at least one of bismuth, cobalt, titanium, nickel and manganese.

[0017] Optionally, a material of at least one of the inner electrode and the outer electrode includes silver and at least one of palladium, gold and platinum.

[0018] The present application also provides an electronic device, comprising the multilayer varistor described in any one of the above items.

[0019] As described above, the present application increases the distance between the inner electrode and the corresponding outer electrode edge by providing a rounded corner at the top corner of the free end of the inner electrode, thereby reducing the risk of the ceramic body (for example, the top corner of the ceramic body corresponding to the rounded corner) being punctured and the resulting load failure; in addition, the rounded corner can also avoid tip discharge, and thus can also help reduce the risk of the ceramic body and the top corner corresponding to the rounded corner being punctured and the resulting load failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of the structure of a stacked varistor provided in an embodiment of the present application;

[0021] Figure 2 A schematic diagram of the stacking arrangement of electrodes in each layer provided in an embodiment of the present application;

[0022] Figure 3 A top view of a first inner electrode and an intermediate inner electrode provided in an embodiment of the present application;

[0023] Figure 4 A schematic diagram of an exploded structure of a multilayer varistor provided in an embodiment of the present application. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be clearly described below in conjunction with specific embodiments and corresponding drawings. Obviously, the embodiments described below are only part of the embodiments of the present application, not all of the embodiments. In the absence of conflict, the following embodiments and their technical features can be combined with each other and also belong to the technical solutions of the present application.

[0025] In the description of the embodiments of the present application, terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", and "counterclockwise" indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the technical solutions of the corresponding embodiments, rather than indicating or implying that a device or element must have a specific orientation, be constructed and operated in a specific orientation, and should not be understood as a limitation on the present application.

[0026] Please also read Figures 1 to 4 1 is a schematic diagram of the structure of a multilayer varistor provided in an embodiment of the present application, and a schematic diagram of a partial structure. The multilayer varistor 1 includes a ceramic body 10 , an external electrode 11 , and a plurality of internal electrodes 12 .

[0027] The shape and size of the multilayer varistor 1 are not limited in the present embodiment. For example, the shape can be Figures 1 to 3 The so-called quasi-cube can be understood as the shape of the multilayer varistor 1 is a rectangular body as a whole, but the vertex is a rounded corner with a predetermined radius of curvature, and the lines forming a single vertex are not two traditional sharp corners. It should be noted that Figures 2 to 4 The figure shows a part of the laminated varistor 1, specifically a structure combining a plurality of internal electrodes 12 and a plurality of resistance layers 10a, while the external electrode 11 is not shown. Figure 2 The number of internal electrodes 12 shown is for exemplary purposes only; Figure 3 What is shown is only the structural shape of the internal electrode 12 when viewed from above.

[0028] The length direction of the stacked varistor 1 is the first direction x, the height direction of the stacked varistor 1 is the second direction y, and the width direction of the stacked varistor 1 is the third direction z. The first direction x, the second direction y and the third direction z are perpendicular to each other and can be regarded as three coordinate axes of a three-dimensional rectangular coordinate system.

[0029] It should be understood that the so-called perpendicularity in the whole application does not require that the angle between the two must be 90°, but allows a deviation of ±10°, that is, the so-called perpendicularity can be understood as the angle between any two directions is 80° to 100°. Similarly, the so-called parallelism in the whole application does not require that the angle between the two must be 0° or 180°, but allows a deviation of ±10°, that is, the so-called parallelism can be understood as the angle between any two directions is 0° to 10° or 170° to 190°.

[0030] like Figure 4 As shown, multiple resistor layers 10a are stacked in sequence to form a ceramic body 10 of the stacked varistor 1. The multiple resistor layers 10a can be composed of semiconductor materials with nonlinear characteristics, for example, they can be a structure formed by stacking multiple cast ceramic diaphragms, and the main component of the ceramic diaphragm can be zinc oxide (ZnO), and contain at least one oxide of bismuth (Bi), cobalt (Co), titanium (Ti), nickel (Ni), manganese (Mn), chromium (Cr), antimony (Sb) and other secondary components with nonlinear characteristics, such as Bi2O3, Co2O3, MnO2, Sb2O3, TiO2, Cr2O3, Ni2O3 and other additives. In some embodiments, the mass proportion of zinc oxide is α, 85%≤α≤95%, which is conducive to ensuring the nonlinear characteristics of the resistor layer 10a and making the resistance value sensitive to the external voltage change good.

[0031] The internal electrodes 12 and the resistance layers 10a are alternately stacked in sequence along the second direction y, for example, by casting, curing, cutting, etc. to form a Figure 4 The bottommost substrate resistance layer 10a is shown, and then a first resistance layer 10a is formed on the substrate resistance layer 10a, and then a first internal electrode 12 is arranged on the first resistance layer 10a, and a second resistance layer 10a is formed on the first internal electrode 12 in the same or similar manner, and the second internal electrode 12 is arranged on the second resistance layer 10a, and so on. Optionally, a structure as shown in FIG. Figure 4 The topmost resistive layer 10a is shown.

[0032] The two adjacent layers of inner electrodes 12 are insulated by a ceramic body (i.e., a resistor layer 10a sandwiched between the two layers of inner electrodes 12), and along the second direction y, these inner electrodes 12 can be rectangular as a whole. However, the difference is that at least part of the inner electrodes 12 are provided with rounded corners. Specifically, the free end not connected to the outer electrode 11 includes a first vertex angle and a second vertex angle, and at least one of the first vertex angle α1 and the second vertex angle α2 is a rounded corner. The so-called rounded corner can be understood as: at least the cross section along the xz direction has an angle (vertex) of a circular arc. Of course, the cross section along the xy direction and the yz direction can also be an angle with a circular arc. The radius of the so-called rounded corner can be understood as: the radius of the circle where the circular arc is located.

[0033] like Figure 1 As shown, the laminated varistor 1 is provided with an external electrode 11, and the external electrode 11 is connected to the corresponding internal electrode 12. The width and shape of the external electrode 11 include but are not limited to Figure 1 As shown, it can be set according to the actual adaptability. In some embodiments, the conductive material of the external electrode 11 can be composed of, for example, silver, gold, palladium, platinum, or an alloy of silver and gold, palladium, platinum, etc.

[0034] The two external electrodes 11 are respectively arranged on opposite sides of the ceramic body 10 along the first direction x; one of any two adjacent internal electrodes 12 is connected to one of the external electrodes 11 (for example, the external electrode 11 on the left), and the other is connected to the other external electrode (for example, the external electrode 11 on the right). Along the second direction y, the orthographic projections of these internal electrodes 121 overlap as a whole, but may not overlap at the vertex position.

[0035] The stacked varistor 1 of the present application can reduce the risk of the ceramic body 10 (for example, the top corner of the ceramic body 10 corresponding to the rounded corner) being punctured and the load failure caused by this by providing the top corner of the free end of the inner electrode 12 with a rounded corner, thereby increasing the distance between the inner electrode 12 and the corresponding edge of the outer electrode 11; in addition, the rounded corner can avoid tip discharge, and can also help reduce the risk of the ceramic body 10 and the top corner corresponding to the rounded corner being punctured and the load failure caused by this. Among them, the edge of the outer electrode 11 can also be regarded as the edge of the ceramic body 10 that is not covered by the outer electrode 11, for example Figure 1 The outer electrode 11 shown is at the junction of the four surfaces of the upper, lower, left and right sides of the ceramic body 10.

[0036] In the laminated varistor 1, optionally, the free ends of at least two internal electrodes 12 are provided with the rounded corners. Figure 2 The two inner electrodes 12 shown in the figure are provided with rounded corners as an example. Figures 2 to 4The multiple inner electrodes 12 include a first inner electrode 121, a second inner electrode 122 and a plurality of intermediate inner electrodes 123, the plurality of intermediate inner electrodes 123 are arranged between the first inner electrode 121 and the second inner electrode 122, and the free ends of the first inner electrode 121 and the second inner electrode 122 are provided with the rounded corners.

[0037] By setting the free ends of the upper and lower two inner electrodes 12 (i.e., the first inner electrode 121 and the second inner electrode 122) of the multiple inner electrodes 12 as rounded corners, the risk of the ceramic body 10 and the vertex corresponding to the rounded corner being broken down and the load failure caused thereby can be reduced. The present application has learned through analysis and research on the laminated varistor 1 that since the current is transmitted toward the inner electrode 12 close to the inside of the ceramic body 10, the current density at the upper and lower two inner electrodes 12 is relatively high, especially the ends (i.e., the free ends) of the two inner electrodes 12 away from the corresponding connected outer electrodes 11. Therefore, increasing the distance between the end and the edge of the corresponding outer electrode 11 can further reduce the risk of the ceramic body 10 and the vertex corresponding to the rounded corner being broken down and the load failure caused thereby.

[0038] In some embodiments, the radius of the fillet of the first inner electrode 121 and the second inner electrode 122 is greater than the radius of the fillet of a conventional inner electrode (e.g., the middle inner electrode 123 of the present application). For example, the first vertex angle α1 is a fillet, and the radius is R1, and 0.25 mm≦R1≦2 mm. Preferably, 0.25 mm≦R1≦1 mm or 0.75 mm≦R1≦1.25 mm.

[0039] Similarly, optionally, the second vertex angle α2 is a rounded angle with a radius of R2, and 0.25 mm≦R2≦2 mm. Preferably, 0.25 mm≦R2≦1 mm or 0.75 mm≦R2≦1.25 mm.

[0040] The first vertex angle α1 and the second vertex angle α2 are both rounded, and the radii of the two are equal.

[0041] Setting the rounded corners of the inner electrode 12 within the above-mentioned size threshold can not only ensure that the risk of load failure caused by breakdown of the top corners of the ceramic body 10 corresponding to the rounded corners is low, but also ensure the overlapping area of ​​all the inner electrodes 12 of the multilayer varistor 1, thereby ensuring the current carrying capacity of the multilayer varistor 1.

[0042] It should be understood that the free ends of a preset number of intermediate inner electrodes 123 in the embodiment of the present application may also be provided with the rounded corners. From another aspect, this design is equivalent to providing a plurality of first inner electrodes 121 and / or a plurality of second inner electrodes 122, thereby reducing the risk of the top corners of the ceramic body 10 corresponding to the rounded corners being punctured and the load failure caused thereby. However, it should be noted that the value of the preset number must ensure the overlapping area of ​​all the inner electrodes 12 of the stacked varistor 1, so as to ensure the current carrying capacity of the stacked varistor 1. For example, the value of the preset number may be 1 or 2.

[0043] In addition, optionally, the non-free end of each inner electrode 12 (ie, the end connected to the outer electrode 11) can also be set to a rounded corner, thereby further reducing the risk of the top corner of the ceramic body 10 being punctured and the resulting load failure.

[0044] In the actual manufacturing scenario, the specific implementation details of each step of forming each structural element of the laminated varistor 1 can refer to the prior art. For example, it can be processed by processes such as molding, cutting, debinding sintering, chamfering, and electroplating. For example, prepare relevant materials that meet the requirements, prepare a ceramic layer (resistance layer 10a) with a conductive pattern, and stack and connect the obtained ceramic layers in a certain regular manner to obtain the required ceramic body 10 containing multiple internal electrodes 12; divide the whole block of several connected ceramic bodies 10 into single ones in a certain cutting method; after separation, treat the independent ceramic body 10 at a certain temperature to discharge excess organic solvent and sinter at a high temperature to obtain the required components with certain electrical characteristics. Silver is dipped in the length direction of the ceramic body 10, and the silver is burned to initially form the external electrode 11, and a nickel layer and a tin layer are sequentially formed outside the external electrode 11 through an electroplating process.

[0045] The technical effect of the present application is illustrated below by comparing Example 1 with Comparative Example 1.

[0046] Please refer to Table 1 below. The dimensions of the multilayer varistors of Example 1 of the present application and Comparative Example 1 of the prior art are equal. Specifically, the length, width and height are 5.9*5.1*2.8 respectively. The rated load working voltage is 85V. The ceramic body materials of both are zinc oxide varistor ceramics, and the internal electrodes are made of silver-palladium alloy materials.

[0047]

[0048] Table 1

[0049] The multilayer varistors of Example 1 of the present application and Comparative Example 1 of the prior art were load tested under the same conditions. For example, the ambient temperature of the load test was 85°C, the humidity was 85%, the load time was 168 hours, and the number of load tests was the same, both 50,000.

[0050]

[0051] Table 2

[0052] Please refer to the load test results shown in Table 2 above. It can be seen that the number of load failures in Example 1 of the present application is 0, while the number of load failures in Comparative Example 1 of the prior art is 5. It can be seen that the present application can significantly reduce or even completely avoid the risk of load failure of the laminated varistor.

[0053] In the multilayer varistor 1 of any of the above embodiments, the ceramic body 10 includes a plurality of vertex angles, wherein the vertex angles closest to the first vertex angle α1 and the second vertex angle α2 may also be rounded. Figures 1 to 4 Taking the rectangular-shaped multilayer varistor 1 as an example, the ceramic body 10 is also a rectangular-shaped body, including 8 rounded corners, and correspondingly, the corners of the two external electrodes 11 covering the 8 corners are also rounded. In other scenarios, only the corners of the ceramic body 10 that are closest to the first corner α1 and the second corner α2 can be rounded, for example, at least only 4 corners can be rounded.

[0054] Continue reading Figure 3 As shown, along the cross section of the xz direction, the radius R0 of the fillet of the ceramic body 10 is less than or equal to the radius R1, R2 of the fillet of the nearest inner electrode 12. Of course, along the cross section of the xy direction and the yz direction, the radius of the fillet of the ceramic body 10 is also R0, which is also less than or equal to the radius R1, R2 of the fillet of the nearest inner electrode 12. Here, compared with the prior art in which the vertex angles of the inner electrode 12 and the ceramic body 10 are both sharp corners, or the inner electrode 12 is a sharp corner and the vertex angle of the nearest ceramic body 10 is a rounded corner, in the present application, on the same cross section, the distance between the fillet of the inner electrode 12 (the first vertex angle α1 and the second vertex angle α2) and the fillet of the nearest ceramic body 10 is equivalent to becoming larger. In other words, the thickness of the ceramic structure on the free end side of the inner electrode 12 is increased, and the anti-breakdown capability is enhanced, so the risk of the corresponding vertex of the ceramic body 10 being broken down and the resulting load failure can be reduced.

[0055] The radius R0 of the rounded corner of the ceramic body 10 can be in the range of 0.2 mm ≤ R0 ≤ 0.5 mm. On the basis of the radius value ranges of the first vertex angle α1 and the second vertex angle α2, setting the rounded corner of the ceramic body 10 within the radius threshold can make the anti-breakdown capability stronger and the load failure risk lower.

[0056] An embodiment of the present application further provides an electronic device, which includes the multilayer varistor 1 of any of the above embodiments, and the multilayer varistor 1 is arranged in a circuit of the electronic device.

[0057] The electronic device can be implemented in various specific forms, for example, smart phones, wearable devices, drones, electric vehicles, electric cleaning tools, energy storage products, electric vehicles, electric bicycles, electric navigation tools and other electronic products. It can be understood by those skilled in the art that, in addition to components specifically used for mobile purposes, the configuration according to the embodiments of the present application can also be applied to fixed-type electronic devices.

[0058] Since the electronic device comprises the multilayer varistor 1 of any of the aforementioned embodiments, the electronic device can produce the beneficial effects of the multilayer varistor 1 of the corresponding embodiment.

[0059] It should be understood that the above description is only a partial embodiment of the present application, and does not limit the patent scope of the present application. For ordinary technicians in this field, all equivalent structural changes made using the contents of this specification and drawings are similarly included in the patent protection scope of the present application.

[0060] Although the terms "first, second", etc. are used herein to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. In addition, the singular forms "one", "an", and "the" are intended to include plural forms as well. The terms "or" and "and / or" are interpreted as inclusive, or mean any one or any combination. Only when the combination of elements, functions, steps, or operations is inherently mutually exclusive in some way, an exception to this definition will occur.

Claims

1. A multilayer varistor, characterized in that: include: Ceramic body; A plurality of inner electrodes are sequentially stacked in the ceramic body along a second direction, and two adjacent layers of the inner electrodes are insulated by the ceramic body, wherein the plurality of inner electrodes include a first inner electrode, a second inner electrode, and a plurality of intermediate inner electrodes, and the plurality of intermediate inner electrodes are arranged between the first inner electrode and the second inner electrode; an outer electrode, the plurality of inner electrodes being connected to the outer electrode respectively; The free ends of the first and second inner electrodes that are not connected to the outer electrode include a first vertex angle and a second vertex angle, at least one of the first and second vertex angles is a rounded corner, and the radius of the rounded corner of the first and second inner electrodes is greater than the radius of the rounded corner of the middle inner electrode.

2. The multilayer varistor according to claim 1, characterized in that: The first vertex angle is a rounded angle with a radius of R1, and 0.25 mm≦R1≦2 mm; and / or, The second vertex angle is a rounded angle with a radius of R2, and 0.25 mm≦R2≦2 mm.

3. The multilayer varistor according to claim 1 or 2, characterized in that: The first vertex angle and the second vertex angle are both rounded, and the radii of the two are equal.

4. The multilayer varistor according to claim 1, characterized in that: The ceramic body includes a plurality of vertex corners, and the vertex corners closest to the first vertex corner and the second vertex corner are rounded corners.

5. The multilayer varistor according to claim 4, characterized in that: The radius of the rounded corner of the ceramic body is smaller than or equal to the radius of the rounded corner of the inner electrode that is most adjacent thereto.

6. The multilayer varistor according to claim 5, characterized in that: The radius of the fillet of the ceramic body is R0, and 0.2 mm≦R0≦0.5 mm.

7. The multilayer varistor according to claim 1, characterized in that: In the multilayer varistor, at least a portion of the free ends of the intermediate inner electrodes are provided with the rounded corners.

8. The multilayer varistor according to claim 1, characterized in that: The stacked varistor comprises two external electrodes, which are respectively arranged on opposite sides of the ceramic body along a first direction, wherein the first direction is perpendicular to the second direction; One of any two adjacent inner electrodes is connected to one of the outer electrodes, and the other is connected to the other outer electrode, wherein the first inner electrode is connected to one of the outer electrodes, and the second inner electrode is connected to the other outer electrode.

9. An electronic device, characterized in that: The electronic device comprises the multilayer varistor according to any one of claims 1 to 8 above.

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